1. Field of the Invention
The present invention relates to a signal detection apparatus which when used for counting pulse signals or the like is enabled to discriminate between signal pulses and noise pulses so as to detect only the signal pulses.
2. Description of the Prior Art
FIG. 1 and FIG. 2 are explanatory diagrams of prior art signal detection apparatus, in which FIG. 1(a) shows an example where a pulse-height discriminator 8 is used. The pulse-height discriminator 8 is adapted to generate an output signal 13 only when the pulse peak of an input pulse signal 11 as shown in FIG. l(b) exceeds a preset discrimination voltage 12, and it is therefore made possible to eliminate such noise pulses 14 which have lower pulse peaks than that of the input pulse signal 11 to be detected.
FIG. 2(a) shows an example where a single-channel pulse-height analyzer 15 is used. The single-channel pulse-height analyzer 15 is adapted to generate an output signal 13 only when the pulse peak of an input pulse signal 11 as shown in FIG. 2(b) comes in between two preset discrimination voltages 16 and 17. Therefore, it is made possible to eliminate such noise pulses 14 whose pulse peaks are lower or higher than that of the input pulse signal 11 to be detected.
Since prior art signal detection apparatus are structured as described above, there have been such problems that it is not possible in the case of FIG. 1 to eliminate noise pulses whose pulse heights are comparable to or higher than that of the signal pulse, and in the case of FIG. 2, to eliminate noise pulses whose pulse peaks are comparable to that of the signal pulse.